CAREER: Designing Functionality Into Two-Dimensional Materials Through Defects, Topology, and Disorder

该职业奖支持通过控制缺陷结构关系，以功能二维材料的计算和理论设计为中心的综合研究和教育活动。缺陷是对材料理想结构的偏离，包括：原子缺失、杂质原子的出现和原子的重新排列。大多数传统的三维半导体材料，比如那些构成计算机晶体管的材料，都是依靠有意地加入缺陷来改变它们的特性，使它们能够按照应用的要求发挥作用。例如，光伏太阳能电池依靠结合缺陷使太阳光转化为电能作为可再生能源。热电材料依靠半导体中的缺陷将热量转化为电能，这种电能用于为太空中的卫星提供动力，也可能用于地球上的废热收集。半导体中缺陷的性质与材料中电子的行为密切相关，而电子的行为受量子力学定律的支配。本研究的目标是开发和应用预测计算工具，以了解缺陷如何控制新兴二维材料的特性，这些材料有应用前景。单原子层厚的石墨烯与类似于原子尺度的铁丝网的碳原子蜂窝状排列就是一个例子。与三维材料相比，二维材料的缺陷-性能关系尚不清楚。在二维材料中，材料结构和电子特性之间存在独特的耦合，导致了不同于三维材料的独特而丰富的缺陷物理。这项研究的结果将是计算工具的发展，以建立这些关系，并加强对二维系统缺陷工程的理解，以帮助在电子，光子学，能量收集和存储以及其他领域实现更好的性能设备。这项研究工作将与教育和外联活动结合起来，以增加下一代技术劳动力的多样性。通过引入一门名为“科学与工程研究人员社区拓展”的新课程，该努力瞄准了从中学生到研究生的学生发展管道的几个关键节点。参加该课程的研究生和本科生将直接参与到当地学校的外展活动。他们将设计、测试、修改、部署并向香槟-厄巴纳地区的当地中学以及伊利诺伊州校园为高中生举办的为期一周的住宿夏令营传播主动学习模块。这些学习活动将通过每年一次的教师培训讲习班和一个专门的在线网站向社区传播。在研究过程中开发的软件将通过GitHub作为开源向更广泛的社区传播。该职业奖支持通过定制缺陷和拓扑结构，以功能二维材料的计算和理论设计为中心的综合研究和教育活动。二维材料的最新进展为电子学、光子学、能量收集和存储以及其他领域的应用提供了有趣的可能性。一个关键的障碍是2D材料中的缺陷表现出与3D材料中的缺陷相同的行为，目前它们还没有得到很好的理解。在二维材料中，拓扑结构和电子结构之间产生了独特的耦合，从而产生了独特而丰富的缺陷物理。这项工作的目标是利用这种独特的耦合，以受控的方式通过有目的地添加缺陷来实现前所未有的功能。为了在二维材料中融合拓扑结构和电子结构的各个方面，PI将调用跨越原子尺度的方法，其中需要基于相互作用薛定谔方程的量子力学描述到微米尺度的拓扑缺陷结构。预测2D材料在3D中变形的缺陷拓扑结构的统计力学框架将直接与第一性原理电子结构方法联系起来，以证明拓扑结构和化学掺杂可以以实现新功能的方式集成。第一性原理方法将利用混合密度泛函理论和新兴的高精度量子蒙特卡罗方法。由于缺陷的定量第一性原理描述需要非常高的准确性，因此将评估可达到的准确性的潜在限制。该综合方法将用于回答二维系统中缺陷物理的几个突出问题。这些包括：(a)如何将拓扑结构和功能化集成到设计高性能二维热电器件中？(b)如何将拓扑结构和化学掺杂结合起来设计高性能的二维光伏电池？(c) 2D材料是否会像3D材料一样经历缺陷介导的韧性/脆性转变？(d)二维材料中缺陷引起的绝缘体到金属转变的性质是什么？这项研究工作将与教育和外联活动结合起来，以增加下一代技术劳动力的多样性。通过引入一门名为“科学与工程研究人员社区拓展”的新课程，该努力瞄准了从中学生到研究生的学生发展管道的几个关键节点。参加该课程的研究生和本科生将直接参与到当地学校的外展活动。他们将设计、测试、修改、部署并向香槟-厄巴纳地区的当地中学以及伊利诺伊州校园为高中生举办的为期一周的住宿夏令营传播主动学习模块。这些学习活动将通过每年一次的教师培训讲习班和一个专门的在线网站向社区传播。在研究过程中开发的软件将通过GitHub作为开源向更广泛的社区传播。

NONTECHNICAL SUMMARYThis CAREER award supports integrated research and education activities centered on computational and theoretical design of functional two-dimensional materials through controlling defect-structure relationships. Defects are deviations from the ideal expected structure of a material and include: missing atoms, the appearance of impurity atoms, and rearrangements of atoms. Most conventional three-dimensional semiconductor materials, such as those that make up the transistors in computers, rely on the intentional incorporation of defects to modify their properties to enable them to function as required for the application. For instance, photovoltaic solar cells rely on incorporation of defects to enable sunlight to electricity conversion as a renewable energy source. Thermoelectric materials rely on defect incorporation into semiconductors to convert heat to electricity, which is used to power satellites in space and may be useful for waste heat harvesting on earth. The properties of defects in semiconductors are closely linked to the behavior of electrons in the material, which is governed by the laws of quantum mechanics. The goal of this research is to develop and apply predictive computational tools to understand how defects control the properties of emerging two-dimensional materials that are promising for applications. Single atomic-layer thick graphene with a honeycomb arrangement of carbon atoms that resembles atomic-scale chicken wire provides one example. In comparison to three-dimensional materials, the defect-property relationships in two-dimensional are not well understood. A unique coupling between material structure and electronic properties arises in 2D materials and leads to a distinct and rich defect physics that is different from 3D materials. The outcomes of this research will be the development of computational tools to establish these relationships, and an enhanced understanding of defect engineering in two-dimensional systems to help realize better performing devices in electronics, photonics, energy harvesting and storage, and other areas. The research effort will be integrated with educational and outreach activities to increase the diversity of the next generation technical workforce. Through the introduction of a new course entitled "Community Outreach for Science and Engineering Researchers," the effort targets several key junctures of the student development pipeline from middle school to graduate students. Graduate and undergraduate students enrolled in the course will be directly engaged in outreach activities to local schools. They will design, test, revise, deploy, and disseminate active learning modules both to local middle schools in the Champaign-Urbana region and at weeklong residential summer camps for high school students held on the Illinois campus. The learning activities will be disseminated to the community through annual teacher training workshops and an online dedicated website. Software developed in the course of the research will be disseminated as open source to the broader community through GitHub.TECHNICAL SUMMARYThis CAREER award supports integrated research and education activities centered on computational and theoretical design of functional two-dimensional materials through tailored defect and topological structure. Recent advances in 2D materials have raised intriguing possibilities with applications in electronics, photonics, energy harvesting and storage, and other areas. A critical barrier is that defects in 2D materials exhibit behavior from those in 3D materials, and currently they are not well understood. A unique coupling between topological structure and electronic structure arises in 2D materials and gives rise to a distinct and rich defect physics. The goal of this work is to exploit this unique coupling to enable unprecedented functionality through the purposeful addition of defects in a controlled way.To merge aspects of topological structure and electronic structure in 2D materials, the PI will invoke approaches that span length scales from the atomic scale where a quantum mechanical description based on the interacting Schrodinger equation is required to micrometer-scale topological defect structures. Statistical mechanics frameworks that predict the defect topology of a 2D material that deforms in 3D will be directly linked with first-principles electronic structure methods to demonstrate that topology and chemical doping can be integrated in ways that enable new functionality. First-principles approaches will utilize both hybrid density functional theory and emerging, high-accuracy quantum Monte Carlo methods. Since quantitative first-principles descriptions of defects require extraordinarily high accuracy, potential limitations to the accuracy attainable will be assessed. The integrated approach will be used to answer several outstanding questions on defect physics in 2D systems. These include: (a) How can topological structure and functionalization be integrated to design high-performance 2D thermoelectrics? (b) How can topological structure and chemical doping be integrated to design high-performance 2D photovoltaics? (c) Do 2D materials undergo defect-mediated ductile/brittle transitions as their 3D counterparts? (d) What is the nature of the defect-induced insulator to metal transitions in 2D materials? The research effort will be integrated with educational and outreach activities to increase the diversity of the next generation technical workforce. Through the introduction of a new course entitled "Community Outreach for Science and Engineering Researchers," the effort targets several key junctures of the student development pipeline from middle school to graduate students. Graduate and undergraduate students enrolled in the course will be directly engaged in outreach activities to local schools. They will design, test, revise, deploy, and disseminate active learning modules both to local middle schools in the Champaign-Urbana region and at weeklong residential summer camps for high school students held on the Illinois campus. The learning activities will be disseminated to the community through annual teacher training workshops and an online dedicated website. Software developed in the course of the research will be disseminated as open source to the broader community through GitHub.